Molten slags include, for example, molten blast furnace slag, molten converter slag, and molten electric furnace slag. It has been known that it is possible to obtain a rapidly cooled solidified slag by cooling a molten slag at a high cooling rate for solidification.
As an apparatus for obtaining a rapidly cooled solidified slag by rapidly cooling and solidifying a molten slag as mentioned above, the following apparatus for manufacturing a rapidly cooled solidified slag is known.
FIG. 1 shows the apparatus for manufacturing a rapidly cooled solidified slag, which is substantially the same as the apparatus for manufacturing a rapidly cooled solidified slag disclosed in the U.S. Pat. No. 4,050,884 dated Sept. 27, 1977. The above-mentioned conventional apparatus for manufacturing a rapidly cooled solidified slag is described below with reference to FIG. 1.
In FIG. 1, the housing 1 is an enclosed-structure having an opening 1a at the top thereof for passing a molten slag, and a discharge port 1b at the lower end thereof, for discharging a crushed rapidly cooled solidified slag 7'. In the housing 1, a pair of cooling drums 2 each having the same diameter and the same length are arranged so that the axial directions thereof are parallel to each other in the same horizontal plane and the peripheral surfaces thereof are in contact with each other. Each of the pair of cooling drums 2 is rotated by a suitable driving means (not shown) in directions opposite to each other at the same peripheral speed as shown by the arrows "a" and "a'" in FIG. 1, in the rising direction of the peripheral surface of each of the pair of cooling drums 2 at the contact portion thereof. A plurality of cooling through-holes (not shown) are pierced in the peripheral wall of each of the pair of cooling drums 2 in the axial direction thereof. One end of each of the plurality of cooling through-holes communicates with a hollow portion (not shown) of one end of the center axle of the cooling drum 2, and the other end of the cooling through-holes communicates with a hollow portion (not shown) of the other end of the center axle of the cooling drum 2. The hollow portion of the above-mentioned one end of the center axle of the cooling drum 2 is liquid-tightly connected to one end of a pipe 3 through a swivel joint (not shown). The other end of the pipe 3 is connected to the inlet of a heat exchanger 4 through another swivel joint (not shown). An end of another pipe 5 is provided with a pump 6 on the way is connected to the outlet of the heat exchanger 4. The other end of the pipe 5 is liquid-tightly connected to one of the hollow portion of the center axle of the cooling drum 2 through a swivel joint (not shown). In FIG. 1, one heat exchanger 4 is shown to be connected to one of the cooling drums 2, however another heat exchanger (not shown) is also connected to the other cooling drum 2 in the same way as mentioned above. Therefore, cooling water for cooling the cooling drum 2 is supplied to the plurality of cooling through-holes of the peripheral wall of the cooling drum 2 through the pipe 5 and the center axle of the cooling drum 2 by means of the pump 6. The cooling water supplied to the plurality of cooling through-holes is heated as described later by means of the heat contained in the molten slag 7 which is adhered to the peripheral surface of the cooling drum 2, and supplied to the heat exchanger 4 through the center axle of the cooling drums 2 and the pipe 3 while partially generating steam. The pressurized steam supplied to the heat exchanger 4 is subjected to heat exchange in the heat exchanger 4 to become a cooling water which is supplied again to the plurality of cooling through-holes of the peripheral wall of the cooling drum 2 by means of the pump 6. Thus, the cooling water circulates through the cooling drum 2 and the heat exchanger 4. On the other hand, the high-pressure steam obtained through heat exchange with the pressurized steam in the heat exchanger 4 drives a turbine 8 which in turn drives an electric power generator 9. The high-pressure steam is cooled by a condenser 10 which is provided in the turbine 9, and thereafter supplied again in liquid state to the heat exchanger 4 by means of a pump 11. Cooling water is supplied in circulation to the condenser 10 from a cooling tower 12 by a pump 13.
A pair of weirs 14 are provided in the upper halves of the both ends of each of the pair of cooling drums 2 so as to be in contact with the both ends of each of the pair of cooling drums 2. In FIG. 1, one of the pair of weirs 14 is shown. The pair of weirs 14 are supported on the housing 1 by means of a suitable supporting means (not shown). A slag sump 15 is formed by the peripheral surface of each of the pair of cooling drums 2 and the pair of weirs 14. The molten slag 7 discharged from the slag runner 16 is poured, through the opening 1a of the housing 1, into the slag sump 15 where a slag pool is formed. The molten slag 7 poured into the slag sump 15 adheres to the peripheral surfaces of the cooling drums during rotation, rapidly cooled and solidified into a rapidly cooled solidified slag. The cooling water supplied to the plurality of cooling through-holes of the peripheral wall of the cooling drum 2 is heated by the molten slag 7 deposited on the peripheral surface of the cooling drum 2 to become a pressurized steam. When the rapidly cooled solidified slag 7' reaches the lower half of the cooling drum 2 along with the rotation of the cooling drum 2, the rapidly cooled solidified slag 7' adhering to the peripheral surface of the cooling drum 2 is peeled off therefrom, while being crushed by a scraper 17 supported on the housing 1 by means of a suitable supporting means (not shown), and drops into the lower part of the housing 1. An opening and closing means (not shown) is provided in the discharge port 1b of the lower part of the housing 1. The peripheral surface of the cooling drum 2 from which the rapidly cooled solidified slag 7' has been peeled off by the scraper 17 comes again into contact with the molten slag 7 of the slag sump 15 along with the rotation of the cooling drum 2, whereby a rapidly cooled solidified slag is continuously manufactured.
According to the above-mentioned apparatus for manufacturing a rapidly cooled solidified slag by using the cooling drum, it is possible to continuously manufacture a rapidly cooled solidified slag, and to recover the heat at a high temperature gained by the cooling drums through the heat exchange with the molten slag.
However, the above-mentioned apparatus for manufacturing a rapidly cooled solidified slag has the following problems. Being always in contact with the both ends of each of the pair of cooling drums 2, the pair of weirs 14 are also cooled. When a molten slag 7 comes into contact with the pair of weirs 14, therefore, the molten slag 7 adheres to the surface of each of the pair of weirs 14, resulting in formation of a solidified slag thereon. Formation of the solidified slag on the slag pool causes decrease in the slag pool temperature and further growth of the solidified slag. As a result, smooth rotation of each of the pair of cooling drums 2 is impaired, and this finally leads to stoppage of the rotation thereof. Also, due to the difference in thermal expansion between the pair of weirs 14 and the pair of cooling drums 2, the contact resistance between the pair of weirs 14 and the pair of cooling drums 2 increases, and this impairs smooth rotation of each of the pair of cooling drums 2.